Dipole antenna elements have become known, for example, from prior publications DE 197 22 742 A and DE 196 27 015 A. The dipole antenna elements may in this case have a normal dipole structure or, for example, may be formed from a cruciform dipole arrangement or a dipole square, etc. A so-called vector cruciform dipole is known, for example, from the prior publication WO 00/39894. The structure appears to be comparable to a dipole square. However, in the end, the specific configuration of the dipole antenna element according to this prior publication creates a cruciform dipole structure from the electrical point of view, so that the antenna element formed in this way can transmit and receive in two mutually orthogonally aligned polarizations. All of these prior publications as well as the other dipole structures which have been known for a long time by the average person skilled in the art are to this extent also included in the content of the present application.
In the past, dipole antenna elements or antenna elements similar to dipoles have generally been positioned on the reflector such that they are electrically, that is to say conductively, connected to the reflector. However, it has already been proposed in commonly-assigned copending published U.S. patent application US2004-0201537A1 that was not published prior to this for an antenna element such as this to be capacitively coupled to the reflector plate. With the interposition of, for example, a non-conductive element, in particular a dielectric, or with the formation of a non-conductive contact section on the antenna element or on its mount device on which the antenna element is placed on the reflector plate, it is thus possible for the antenna element to be positioned on the reflector in a uniquely reproducible manner from the electrical point of view, since this avoids the intermodulation problems which occur in some circumstances according to the prior art. This is because, when a dipole or antenna elements which are similar to dipoles were mechanically mounted on the reflector plate according to the prior art, they were normally fitted to the reflector plate by means of screws or other connecting mechanisms, thus making it possible for different contact conditions to occur, depending on the installation accuracy, with the consequence that intermodulation problems could occur, which express themselves in different ways.
It is also desirable to take into account the fact that in the majority of all cases, the dipoles or antenna elements similar to dipoles are placed on the reflector plate and are mounted from the reflector rear face by screwing in one or more screws. However, if the contact pressure also decreases, for example because of heat influences, then the contact conditions change, thus resulting in a significant decrease in the performance of an antenna element such as this.
According to US2004-0201537A1, while avoiding an electrically conductive contact by using capacitive coupling, it is also possible to achieve the further advantage that no voltage potential can occur between the dipole and the reflector. This is because the differently chosen materials for a dipole antenna element or for the mount device for a dipole antenna element and the material for the reflector conventionally otherwise result in an electrochemical voltage which can lead to contact corrosion. Since the exemplary illustrative non-limiting implementation herein avoids this, this also results in a greater range of possible selections for the materials which can be used for the dipole and/or for the reflector.
The exemplary illustrative non-limiting implementation will be described in the following text with reference to a so-called vector dipole, whose fundamental configuration is known from WO 00/39894, whose entire disclosure content is referred to. However, the exemplary illustrative non-limiting implementation herein can be applied to all dipoles, for example also to cruciform dipoles or simple dipoles, such as those which are known from DE 197 22 742 A1, DE 198 23 749 A1, DE 101 50 150 A1 or, for example, U.S. Pat. No. 5,710,569.
The exemplary illustrative non-limiting implementation herein thus provides a further improved antenna with capacitive coupling between the antenna element or its mount device and an associated conductive reflector or a conductive reflector surface.
The present exemplary illustrative non-limiting implementation herein results in a significant improvement in comparison to conventional antennas that are known from the prior art. In this case, the present exemplary illustrative non-limiting implementation represents another more far-reaching improvement even in comparison to the solution which was mentioned above but was not published prior to this, according to which capacitive coupling of the antenna to the reflector was already provided.
The exemplary illustrative non-limiting implementation now provides an electrically conductive coupling element which projects in the form of a rod from the reflector and is preferably electrically conductively connected to the reflector plate. The actual antenna element device can be placed on this. Generally, the mount device to which the dipole antenna element or the antenna element structure in the form of a dipole is fitted, has an axial recess by means of which the mount device can be placed on the coupling element. The coupling element may be in the form of a rod. Although the coupling element which is in the form of a rod enters the axial recess in the mount device and generally comes to rest coaxially in the axial recess in the mount device, the coupling element which is in the form of a rod is electrically conductively isolated from the conductive mount device. This results inter alia in capacitive and/or possibly inductive outer conductor coupling between the reflector and the coupling element, which is preferably electrically conductively connected to the reflector, on the one hand, and the electrically conductive part of the mount device.
In one preferred exemplary illustrative non-limiting implementation, the electrically conductive coupling element which is in the form of a rod is in this case in the form of a tubular body, which can be soldered, welded or mounted in some other way on the reflector plate. A hollow-cylindrical sleeve which acts as an insulator or some other illustrated spacer is then just pushed onto the coupling element which is in the form of a rod, a flange preferably being formed at the lower end of this sleeve which acts as the dielectric, and the conductive mount device for the antenna element structure can be pushed on as far as this flange.
However, in a development of the exemplary illustrative non-limiting implementation, air may also be used as the dielectric. One can do this by using specific spacers to ensure that the electrically conductive mount device which is fitted does not make an electrically conductive contact with the reflector, and/or with the coupling element which is in the form of a rod and is electrically connected to the reflector.
In principle, it is also possible for the electrical mount device itself to be formed from non-conductive material, for example plastic. An electrically conductive covering may be drawn over it on the outside. The mount device can then be placed onto the electrically conductive coupling element, which is in the form of a rod, with a sliding face. Preferably, a small amount of play may be provided with the length of the coupling elements which are in the form of rods, also making it possible to ensure that the lower end of the mount device, adjacent to the reflector, cannot make contact with the reflector. Alternatively or in combination, an insulating layer may likewise be formed or provided here, or the end wall of the mount device is not provided with an electrical outer layer at this point.
As has been mentioned, the coupling element which is in the form of a rod is preferably hollow or is hollow-cylindrical. A corresponding recess is provided, axial in line with respect to it, in the reflector. This makes it possible to connect the outer conductor of a coaxial cable for feeding the antenna element arrangement to the reflector plate on its rear face, and/or to connect it to the tubular attachment, which may also project on the lower face, of the electrically conductive coupling element which is in the form of a rod (generally to be connected electrically conductively, for example by soldering), and to pass the inner conductor coaxially through the coupling element which is in the form of a rod upwards, such that it is electrically isolated from it in order to connect the inner conductor in some suitable manner there, that is to say in general to electrically connect it to the opposite dipole half.
In a development of the exemplary illustrative non-limiting implementation, an electrical element which is in the form of a rod and is integrated firmly there may be provided for the inner conductor in the coupling element which is in the form of a rod, so that the inner conductor is connected at the bottom. However, the inner conductor may also be laid upwards as an extended inner conductor in the form of a cable through the element which is in the form of a rod, preferably with the interposition of an isolator.
However, it is also possible to pass an inner conductor in its entirety through the element which is in the form of a rod and to connect the outer conductor located at the top to the element which is in the form of a rod and, separately from this, to design the inner conductor such that it is lengthened with respect to the dipole half that is generally opposite or to make electrical contact with an electrical connecting bracket in the immediate physical vicinity, in order to make electrical contact with the outer conductor, with this connecting bracket producing a connection for the opposite dipole half.
However, fundamentally, it is also possible to reverse the coupling principle. Specifically, the coupling element may be in the form of an outer pot part which is conductively connected to the reflector. The mount section of the dipole is positioned in the interior of this by means of an isolator, by means of air or in some other suitable manner, in order to achieve the coupling, which is primarily referred to as capacitive outer conductor coupling.
A wide range of further modifications, some of which will also be explained in detail in the description, are possible.
Finally, in one preferred exemplary illustrative non-limiting implementation, it is likewise possible to likewise design the inner conductor contact to be capacitive.